1. Field of the Invention
The present invention relates to multiplex, intensifier, piston-type pumps which are hydraulically driven and which are especially suitable for pumping mud and other well fluids in the drilling, completion, and workover of oil and gas wells.
2. Description of the Prior Art
Hydraulically driven pumps are known in the art. The plunger in each pump unit is driven by a fluid. One undesirable characteristic of prior pump designs has been the pulsating discharge and suction of such pumps. Various schemes have been employed in an attempt to overcome this pulsating characteristic such as increasing the number of acting pistons or plungers and overlapping their strokes, or by providing a surge chamber in which the pump fluid is accumulated and discharged at stroke reversal. Controls for returning the hydraulic piston are complex. As a result of the above designed changes, the cost and complexity of the pumping units has increased considerably.